1. Field of the Invention
The present invention relates to a transistor, a process of producing it, to a light-emitting device, and to a display. More particularly, the present invention relates to a transistor capable of modulating, at low voltages, a large current flowing between the emitter and the collector, to a process of producing the transistor, to a light-emitting device comprising the transistor, and to a display comprising the transistor.
2. Background Art
Although some displays using organic transistors, produced on an experimental basis, have been reported in recent years, many of them are combinations of organic field-effect transistors (organic FETs) and liquid crystals or electrophoretic cells, and there have been reported few displays using organic EL devices. This is because it is not easy for the present organic FETs to allow currents large enough to switch organic EL devices, current-driven devices, to flow. There is therefore a demand for development of organic FETs that operate at lower voltages and with larger currents.
In order to fulfill the above demand, it is necessary to decrease the channel length, when the mobility of the known organic materials are taken into account. However, with patterning techniques useful for the mass production of displays, it is difficult to decrease the channel length to below several micrometers. In order to solve this problem, studies have been made on “vertical transistor structures”, in which currents flow along the film thickness to make the transistors operable at lower voltages and with larger currents. Generally, the thickness of a sandwich transistor is several tens nanometers, and, moreover, it can be controlled with high accuracy of several angstroms. It is therefore easy to attain a shorter channel with a length of 1 μm or less by forming the channel along the film thickness. Polymer grid triode structures, static induction transistors (SITs), etc. have been proposed as such vertical organic transistors.
Recently, there has been proposed an organic transistor excellent in transistor performance that can be produced only by making a simple semiconductor/metal/semiconductor layered structure (see non-Patent Document 1). In such an organic transistor, electrons injected from the emitter electrode pass through the intermediate metal electrode to cause current amplification comparable to that with bipolar transistors. Since the intermediate metal electrode works like the base electrode, this organic transistor is called the metal-base organic transistor (MBOT). However, the semiconductor/metal/semiconductor layered structure has not always provided the above transistor action.    Non-Patent Document 1: S. Fujimoto, K. Nakayama and M. Yokoyama, Appl. Phys. Lett., 87, 133503 (2005).